In this description, the term ‘materials’ may include personnel as well as cargo.
Materials handling systems which comprise ladders and trolleys are known. These comprise single length ladders, or ladders which extend by one sliding over another creating a step at the junctions. The former have limited length and the latter are not relatively strong reducing the weight of materials which may be moved along them. It is desirable to have a system which can provide longer lengths without loss of strength.